1. Field of the Invention
This invention relates to devices for locking joints for tubular members. More particularly, the present invention relates to gaskets for sealing and locking a socket end of one tubular to a spigot end of another tubular.
2. Description of the Prior Art
Pipes joined in telescoping relationship typically have a spigot end of one pipe inserted into the socket end of the engaging pipe. The socket end has an opening large enough to receive the spigot end of the enclosed pipe. A gasket is inserted in the socket end of the enclosing pipe and prevents leakage of fluid from the joint by forming a seal between the two pipes. In many applications, a fluid under pressure flows through the pipes. This fluid pressure can produce a separating force, known as joint separating end thrust, that can cause the pipes to separate at the joint.
One method of locking the joint between two pipes involves configuring as sealing gasket as a restraining mechanism. For example, a resilient sealing gasket can be provided with a number of circumferentially spaced apart metal inserts. These metal inserts include teeth that are adapted to penetrate an outer surface of a pipe spigot end. Upon installation, the teeth bite into the pipe spigot end to prevent the pipe spigot end from sliding out of the socket end. As is known, the dimensions of the pipe spigot and socket ends, while conforming to industry standards, can vary during manufacture. The ability of the gasket to seal and lock the joint, however, can be adversely affected by such dimensional variations. Thus, there is a persistent need for sealing and restraining gaskets that can accommodate pipes having such dimensional variations. Moreover, there is a persistent need for gaskets that lock or retain a joint without unduly compromising the structure of the pipe (e.g., excessive penetration). The present invention addresses these and other needs of the prior art.